The present invention relates to a method for manufacturing optical fiber.
Conventionally, an optical fiber is made by first manufacturing a fiber preform, and during this manufacturing process variations occur in the fiber V-number, the V-number being dependent on the fiber core diameter and the fiber delta number, the delta number being indicative of an index of refraction difference between the fiber core and cladding, e.g. (N.sub.1 -N.sub.2)/N.sub.1. Variations in the V-number, the core diameter and the delta number remain in the fiber when it is drawn to a desired outside diameter, typically 125 microns for telecommunication fiber.
If such a fiber is to be used in a distribution system whereby light is tapped from the fiber by passing the light through a coating (e.g. buffer) of the fiber and into an optical coupler at a bend, the amount of light withdrawn and detected by any given tap varies from fiber to fiber and even along a length of any given fiber since the amount of light withdrawn is dependent on the fiber V-number and other parameters which are not held constant during fiber manufacture. This problem exists principally since a fiber parameter typically held constant is the fiber cladding outside diameter which results in the bend loss characteristic being variable due to variations in the fiber V-number. Tap power variations caused by changing bend loss characteristics require that a receiver for the tap have an unduly large dynamic range and an unduly small sensitivity.